One-dimensional, high aspect ratio flexible structures, such as micro- and nanofibers, offer various advantages. In one aspect, the properties, geometry and composition of micro- and nanofibers can be controlled at the micron and sub-micron length scales (Jun, et al., 2014, Lab Chip 14:2145; Li & Xia, 2004, Adv. Mater. 16:1151). In another aspect, these fibers can be used at larger length scales to create complex assemblies and three-dimensional architectures, such as meshes and textiles (Burger, et al., 2006, Annu. Rev. Mater. Res. 36:333; Onoe, et al., 2013, Nat. Mater. 12:584).
Approaches that add versatility and functionality to micro- and nanofibers would allow for the creation of ‘smart’ materials useful within life science and materials science applications. The utilization of composite structures is a common approach to add such multifunctionality. Composite fiber structures with tailored volume fractions of components, precise spatial control, and controlled chemistry and loading of cargo are appealing for many applications, such as scaffolds for the spatial control of cellular microenvironments in tissue engineering (Yamada, et al., 2012, Soft Matter 8:3122; Yamada, et al., 2012, Biomaterials 33:8304), local delivery of therapeutics for wound healing applications (Zahedi, et al., 2010, Polymer. Adv. Tech. 21:77; Zilberman, et al., 2009, J. Biomed. Mater. Res. A 89A:654), immobilization and protection of bacteria in bioreactors (Nardi, et al., 2012, J. Environ. Prot. 3:164), self-healing composite materials for load bearing applications (Sinha-Ray, et al., 2012, J. Mater. Chem. 22:9138), and food science (Arecchi, et al., 2010, J. Food Sci. 75:N80; Sultana, et al., Int. J. Food Microbiol. 62:47).
An exemplary approach for generating composite fibers is to use an emulsion as the pre-fiber solution (Arecchi, et al., 2010, J. Food Sci. 75:N80; Sultana, et al., Int. J. Food Microbiol. 62:47; Dong, et al., 2009, Small 5:1508; Sanders, et al., 2003, Macromolecules 36:3803; Sy, et al., 2009, Adv. Mater. 21:1814; Korehei & Kadla, 2013, J. Appl. Microbiol. 114:1425; Kriegel, et al., 2009, Langmuir 25:1154). Using this process, cargos such as proteins, antimicrobial compounds, and self-healing compounds have been incorporated into electrospun nanofibers. To avoid the mechanical stresses associated with bulk emulsification techniques on fragile cargo, as are results of use of homogenizers and ultrasonication, other techniques have been developed, such as compound-jet electrospinning, coaxial electrospinning, thermally induced in-fiber emulsification of an extruded core-shell fiber, coaxial microfluidics, microfluidics incorporating stratified flows for mosaicked fibers, and valve-based microfluidics for coded fibers. These techniques can generate micro/nanofibers containing various cargos, including cells, drugs, and proteins.
Some methods for producing composite fibers, such as using bulk emulsification, are relatively simple to execute, but lack the spatial control desired for advanced applications. Others, while efficient at fabricating fibers with complex morphologies and a high level of spatial control, rely on complex device designs and externally controlled actuation.
There is a need in the art for novel methods and devices for preparing multi-compartment nano- and microfibers comprising embedded droplets along the length of the fibers. In certain aspects, such methods and devices should allow for control over the spacing of the embedded droplets along the length of the fiber. In other aspects, such methods and devices should allow for encapsulation of components in distinct microcompartments. This provides controlled storage, dissolution and/or delivery of the components. The present invention meets this need.